SMT Soldering: The Precision Control Technique for Solder Paste and Solder Quantity

In the global electronics product market, the demands for miniaturization and high performance are growing rapidly. According to the statistical data of market research institutions, over the past five years, the average size of electronic products has decreased by about 20%, while their performance has increased by more than 30%. This trend has made Surface Mount Technology (SMT) play an increasingly crucial role in the electronics manufacturing industry. In the SMT process, the amount of solder paste used directly determines the quality and reliability of solder joints. Therefore, under specific soldering requirements, locally increasing the amount of solder paste or solder has become an important research direction in the industry.

In some specific scenarios, it is quite necessary to locally increase the amount of solder paste or solder. For example, in the manufacturing of 5G base station circuit boards, the power consumption of heat - generating components such as power amplifiers is 50% higher than that of traditional components. A well - known communication equipment manufacturer found that when producing 5G base station circuit boards, by increasing the amount of solder, the thermal conductivity efficiency can be increased by 30%, effectively ensuring the stable operation of components, reducing the failure rate caused by overheating, and increasing the signal stability of 5G base stations by 25%.

In the automotive electronics field, mechanical stresses such as vibration and impact are common problems. An automotive electronics parts supplier, when producing the engine control unit (ECU) of a car, increased the amount of solder by 20% at the parts 承受 mechanical stress. After simulated vibration tests, the mechanical strength of the solder joints increased by about 40%, greatly enhancing the reliability of the ECU under complex working conditions and reducing the product recall risk caused by solder joint fractures. The recall rate decreased by 35%.

In addition, with the development of electronic technology, the pin pitch of some high - end chips has been reduced to less than 0.3mm. A semiconductor packaging enterprise, when processing chips with a pin pitch of 0.25mm, due to the size deviation between the component pins and the PCB pads, after increasing an appropriate amount of solder, the connection reliability increased from 85% to 95%, effectively ensuring the normal operation of the chips.

To achieve the increase in the amount of solder paste or solder locally, the industry has explored a variety of effective methods.

Adjusting the stencil opening size is a commonly used method. An electronics manufacturing enterprise, when producing smartphone motherboards, enlarged the stencil opening size corresponding to the pads that required more solder by 15%, and the deposition amount of solder paste increased by 20%, effectively improving the solder joint quality. Using trapezoidal or racetrack - shaped openings can deposit 20% more solder paste at the edges of the pads. However, if this method is not properly operated, it may lead to a decline in printing quality. For example, when the solder paste thickness deviation exceeds ±10μm, the soldering defect rate will increase from 3% to 8%.

Multiple printing can precisely control the additional amount of solder. A tablet computer manufacturer, during the production process, performed two - time printing on the same PCB, and each printing increased the solder paste thickness by 12μm, successfully solving the problem of unstable soldering of large - size chips. But multiple printing extends the production time by 2.5 times and increases the cost by 20%.

Using solder pre - forms can precisely control the amount of solder. In the soldering of high - power power modules, an enterprise can precisely control the amount of solder within ±0.05mg. However, the manual placement efficiency is low, and the placement time for each solder joint is about 4 seconds, which greatly limits the production efficiency. If automated placement is adopted, although the efficiency can be improved, additional equipment investment and programming are required, and the equipment procurement cost is approximately 500,000 yuan.

Solder dipping or wave soldering can quickly increase a large amount of solder. When a home appliance enterprise is producing TV motherboards, for through - hole components, the solder dipping process is adopted, and the amount of solder at the solder joints can be increased within 1.5 seconds, improving the production efficiency. But this method is not suitable for chip components with a size of 0402 and below, and improper control may lead to solder bridging. When the bridging rate exceeds 3%, the product non - compliance rate will increase from 5% to 12%.

Adjusting the metal content and rheological properties of solder paste can achieve a higher amount of solder after reflow without changing the stencil design. An electronic component manufacturer used solder paste with a 5% increase in metal content, and the amount of solder after reflow increased by 18%. However, the cost of this special solder paste is 25% higher than that of ordinary solder paste, and it may affect the reflow curve and the overall process, requiring the re - debugging of the production process.

Experts point out that when deciding to locally increase the amount of solder paste or solder in the SMT process, it is necessary to carefully weigh the advantages and potential defects of each method. Each method has its applicable scenarios, and usually, multiple methods need to be combined to achieve the goal. In actual operation, engineers should comprehensively evaluate the specific requirements of the assembly process, component characteristics, as well as the impacts on production efficiency and cost.

The development and application of this technology will strongly promote the electronics manufacturing industry to achieve new leaps in product quality and performance, and provide a solid support for the further innovation of electronic products.